Chemical substances are often called 'pure' to set them apart from mixtures. A common example of a chemical substance is pure water; it has the same properties and the same ratio of hydrogen to oxygen whether it is isolated from a river or made in a laboratory.
It acts to replace and recover from the activities of living. Its action is (almost always) the opposite of the sympathetic division. It activates the gut for digestion, slows the heart rate, decreases the blood pressure, etc. The autonomic nervous system controls the insides of the body: the viscera or gut.
Describe the components of the sympathetic autonomic motor pathway to include: neurons (preganglionic, postganglionic), synapses, ganglia, myelination (type B and type C neurons), effectors, and neurotransmitters (acetylcholine, norepinephrine).